Hope this isn't too late to help with your show! I was just in a production
of Cabaret, and the props crew actually had *4* matching glasses -
two that were hidden behind Cliff's typewriter. Sally cracked real eggs into
the two glasses in view of the audience, then finished making the "Prairie
Oysters" behind the typewriter - switching the glasses in the process.
Audience members swore that they thought our actors had actually drunk
raw eggs.
As to the glasses - they were only juice glass size and tinted (I think ours
were red).
The typewriter case was left on the table, by the way (one of those lovely
old 'portable' ones), which kept the extra glasses hidden until we struck
for the next scene.

The only tough work would then making sure to wash the glasses after
every show & keeping the eggs refrigerated. (And it surely goes without
saying - have more than just the 4 matching glasses!)

And if that doesn't work for you - for the fake eggs perhaps you could
make jello yolks mixed w/ orange juice instead of water?

Best of luck!
closetdiva